| 摘要 |
PURPOSE:To make the share of differential pressure allotted to an adjustment valve and a protective adjustment valve smaller than 50% of the maximum differential pressure, by controlling the protective adjustment valve on the basis of the deviation between an input signal from a differential pressure signal generator and a set value. CONSTITUTION:Pressure detecting pipes 3, 3a are extended respectively from the inlet side and the outlet side of an adjustment valve 1 and connected to a differential pressure signal generator 4. The output signal of the differential pressure signal generator 4 is transmitted to a differential pressure adjuster 5, the output signal of which is in turn applied to a protective adjustment valve 2 as an adjustment signal for the same. With such an arrangement, when the opening of the adjustment valve 1 becomes smaller than about 50% of the maximum opening, differential pressure across the same exceeds 50% of the maximum valve. Under such circumstances, the differential pressure adjuster 5 gives a valve closing signal on the basis of the deviation between the output signal of the signal generator 4 and a set value, so as to reduce the opening of the valve 2 to keep the differential pressure at 50% of the maximum value. |
